When making tunnels of large dimensions and also of considerable length, it is common practice to use a xe2x80x9ctunnel borerxe2x80x9d enabling the entire cutting front to be bored simultaneously. The tunnel borer proper is fitted with a follower train made up of trailers in the form of small cars pulled by the tunnel borer. These trailers are used firstly for transporting various elements that are needed for making the tunnel while it is being bored, such as voussoirs which are put into place to prop up the tunnel wall, and also to remove the cuttings that result from the tunnel boring action proper.
These trailers are fitted with wheels that run directly on the cylindrical wall of the tunnel without any guide rails being interposed. It will be understood that if a trailer is not loaded symmetrically about its longitudinal plane or if the tunnel presents a degree of curvature in a horizontal plane, then the wheels of trailers which are not swivel-mounted will cause the entire trailer to take on a certain amount of tilt, which must be corrected. It will be understood that for proper operation, it is necessary for the trailers of a follower train to be substantially horizontal, in particular for satisfactory transfer of the cuttings that are extracted by the tunnel borer.
There therefore exists a real need to have a system which enables a trailer of a follower train to be maintained substantially horizontal while nevertheless constituting a technique that is simple and that acts simply.
An object of the present invention is to provide a trailer for a tunnel borer follower train satisfying the conditions specified above.
According to the invention, this object is achieved by a trailer for a tunnel borer follower train, the trailer comprising a chassis provided with a plurality of wheels defining an advance direction for the trailer, said chassis at rest presenting a longitudinal axis and a longitudinal plane of symmetry that is vertical, the trailer further comprising:
at least two tanks mounted on the chassis substantially symmetrically about the longitudinal plane of symmetry of the chassis;
means for measuring any tilt of the chassis of the trailer relative to the horizontal about its longitudinal axis;
means for feeding the two tanks with liquid; and
means for controlling the quantity of liquid in each tank as a function of any measured tilt in such a manner that the quantity of liquid contained in each tank creates a return torque about the longitudinal axis tending to compensate any tilt of said trailer.
It will be understood that by permanently controlling the mass of liquid in each of the side tanks of the trailer, it is possible to create a return torque as a function of the indications from the tilt meter fitted to the trailer so as to establish a return torque which enables the trailer to be returned progressively to a substantially horizontal position as it advances. The chassis of the trailer is returned to the horizontal position by its wheels slipping sideways under the effect of the return torque. It will also be understood that the system does not have any complex components, but merely the tanks for receiving and storing the liquid and systems of solenoid valves controlled by a central unit so as to adjust the volume of liquid contained in each of the two tanks.
In a preferred embodiment, the liquid used for filling the tanks in controlled manner is the same as the liquid used for feeding the cooling circuit of the tunnel borer itself.
It will be understood that in this embodiment, the liquid used performs two functions, namely that of cooling the tunnel borer and also that of enabling a return torque to be established for keeping the trailer of the tunnel borer follower train substantially horizontal.